It is well known in the art to utilize a light beam as a sighting aid for weapons. An illumination source is provided that projects a narrow beam of light in a direction parallel to the weapon boresight. When light beam and boresight are properly aligned, the bullet impact will be on or very close to the location of the light spot on the target. Light beam sighting aids are particularly useful at night when ordinary iron or telescopic sights are difficult to use because of low ambient and/or target illumination levels.
Lasers are the preferred means of generating light beams for sighting applications. They have comparatively high intensity, small spot size, and can be focused into a narrow beam with a very small divergence angle. Laser sights for weapons are well known in the art.
Heretofore, laser sights have been comparatively bulky and mounted outside of the weapon. With long guns, the bulk required for the laser sight is small compared to the size of the gun, that is, the additional volume and weight are a small percentage of the volume and weight of the gun itself. However, with hand guns, the typical externally mounted laser sight is a significant fraction of the volume of the gun itself and a gun with such a sight cannot generally be carried in a conventional holster. This is a great disadvantage, both because of the additional space required for the laser sight, and also because the externally mounted laser sight is comparatively easily damaged or knocked out of alignment. In police and military applications, there is a great premium on compact and extremely rugged weapons. Thus, there is a great desire to have a laser sight which is internal to the weapon so as to be protected from rough handling and which does not add to the bulk of the weapon.
In U.S. Pat. No. 4,934,086, Houde-Walter describes an arrangement in which an internal laser light source is provided within an automatic pistol. A laser diode or fiber-optic light conductor coupled to a laser diode is mounted so as to project the laser light beam along the bore of a hollow recoil spring guide tube. The recoil spring guide tube is located within the weapon beneath and parallel to the barrel. A light beam emanating from the recoil spring guide tube projects forward in the same general direction as the bullet travels. The battery and other electronics necessary to power the laser diode in Houde-Walter's arrangement, are mounted in the butt of the weapon.
A disadvantage of this arrangement is that substantial modification of the weapon may be needed to accommodate the battery, drive circuitry, and fiber-optic or electrical connections leading up to the recoil spring guide tube. As a practical matter, modification of a weapon to accommodate such spaced-apart or remotely located components may require a skilled gun smith. This limits the applicability of such an internal laser sight arrangement to those who can afford such modifications to their weapons, and to weapons which have sufficient un-used space within the butt or frame to accommodate the spaced-apart components.
Thus, there continues to be a need for a compact, internally mounted laser sight for hand guns, especially for a laser sight that is adapted to fit a wide variety of weapons and which may be installed by ordinary users without need for an expert gun smith and without significant structural modification of the weapon.